A few companies created a profitable niche, with data driven analytics and promotion. 

Most passive investors are not just buying for the preferred return, rather they are looking for the complete IRR from the deal which is primarily driven by forced price appreciation and possibly loan paydown.

Are there some alternatives to this mainstream, W-2 income driven, lending method?

What about the guy who's from your market, who's driven to meet you face-to-face (several times), had lunch with you, and golfs with your dad every month?

As much as a I would love to be the one you build your portfolio with, there is no better story you could ever tell me than the one you told here.  

I've looked and researched and have even driven for dollars and saw one property so far.

Had I not driven by at that time, I probably never would have figured out why there was going to be ice all over the bottom half of the driveway from the 2nd year of ownership on because I had never thought to take before pictures of the perimeter of the yard.

Welcome @Francis A. . I

But that being said, the OP asked why would anyone sell a good asset and while I agree with what you say, I've seen plenty of transactions driven by ego!

In this example, House A is the Cash house owner, House B is the leveraged 2-house owner.